So how do I write an intellegent freelancing contract so I can keep a roof over my head?

I have been wary of businessmen since I read Catch-22 in middle school, but it is a bit difficult to avoid them and eat for any extended period of time. I want to know what to look for in a freelance contract for programming work and what to include if I have the opportunity to write one myself. I imagine many of you have been in my situation; I appreciate your help. In the absence of experience, idle speculation will do. (edit: Let me recommend middle schoolers avoid Catch-22)